On the other hand, I confess that finding myself on Luboš's blog, with the freedom to write whatever I please, feels a little like finding myself in front of an open mic at the Republican National Convention. One part of me feels a moral obligation to seize this rare opportunity and say something like the following:

CONSERVATIVE LUBOŠ FANS: GET OUT OF YOUR BUBBLE! GLOBAL WARMING IS A REAL PROBLEM! IT'S HAPPENING, HUMAN ACTIVITY IS A MAJOR CAUSE, AND THE CONSEQUENCES ARE SERIOUS! EVEN LUBOŠ'S OWN STRING-THEORIST HEROES, LIKE ED WITTEN AND BRIAN GREENE, BELIEVE SO! VIRTUALLY EVERY SERIOUS SCIENTIST DOES — AT SOME LEVEL, ONE SUSPECTS, EVEN LUBOŠ HIMSELF! BUT HE CAN'T ADMIT IT, BECAUSE HE ASSOCIATES CONCERN ABOUT GLOBAL WARMING – OR ANY OTHER "LEFTY" CAUSE – WITH THE EVIL COMMUNISTS WHO OPPRESSED CZECHOSLOVAKIA IN HIS CHILDHOOD! BUT SOME US DESPISE COMMUNISTS EVERY BIT AS MUCH AS LUBOŠ DOES, BUT ALSO RECOGNIZE THAT THEY'RE NOT THE ONLY EVIL THE WORLD HAS EVER KNOWN! ONE HOPES LUBOŠ WILL EVENTUALLY COME TO THAT REALIZATION AS WELL!

But enough of this. I don't want to abuse my host's hospitality. Luboš invited me here, not to dispute his views on climate change, but rather to promote my new book Quantum Computing Since Democritus (published by Cambridge University Press and available now in Europe, on April 30th in North America, and wherever and whenever on Kindle). So promoting my book is exactly what I'll do—by first telling you the story (such as it is) of my interaction with Luboš, and then explaining how that story relates to the book.

While I've never had the privilege of meeting Luboš in person (those who have tell me he's a perfect gentleman), he and I have ... exchanged pleasantries online. Regulars on the science blogosphere might remember that six years ago, I wrote a tongue-in-cheek blog post recounting my visit to the string theory group at Stanford, and claiming that my "allegiances" in the battle between string theory and loop quantum gravity were now open for sale to the highest bidder. ("Fly me to an exotic enough location, put me up in a swank enough hotel, and the number of spacetime dimensions can be anything you want it to be...")

It is absolutely impossible for me to hide how intensely I despise people like Scott Aaronson ... He's the ultimate example of a complete moral breakdown of a scientist. It is astonishing that the situation became so bad that the people are not only corrupt and dishonest but they proudly announce this fact on their blogs ... [Scott is] a corrupt piece of moral trash. My anger may be quiet but it is unyielding. It's not just him: the Academia is literally flooded by intellectual prostitutes.

Fortunately, Luboš's opinion of me seemed gradually to improve in the ensuing years (I guess it would be hard for it to worsen). For example, in his comments disputing my take on the so-called "PBR Theorem"—I considered the theorem simple and unsurprising but still well worth knowing, while Luboš considered it "garbage" and "crackpot"—Luboš at least upgraded me from "moral trash" to a "mad engineer." (Once again, the irony seemed lost on Luboš: I've never met a real engineer who considered me anything other than a hyper-abstract pure mathematician. I guess if you live in Manhattan, Brooklyn seems like a primitive wilderness.)

Later, Luboš and I discovered that we shared a common enemy, in the countless armchair physicists who notice the profound conflict between their intuitions about how the world should work, and quantum mechanics' description of how it does work—and immediately conclude that the problem must lie with quantum mechanics. Luboš and I were unitedagainst the entanglement-denier Joy Christian, and againagainst the trivial errors of Ross Anderson and Robert Brady. The latter alliance even led Luboš to compliment me, to which I responded as follows:

Luboš says he’s sure my "thinking engines" are good enough to see eye-to-eye with him! Callooh! Callay! This might be the single greatest compliment I’ve ever received.

And Luboš, in return for your generous compliment, I have some good news. As a result of major life changes—getting married, having a baby, etc.—I have abandoned my previous materialistic, money-grubbing ways. I’m now strictly a man of principle. And as such, no amount of money could ever induce me to abandon my total, principled commitment to Loop Quantum Gravity.

OK, OK, I’m kidding about the last part. In fact, I have a much better appreciation now for the achievements of string theory than I did back in 2006, partly due to a meeting in Florence where Brian Greene spent 4 hours explaining them to me and others. I came away genuinely impressed, convinced that string theory and especially AdS/CFT are unequivocally a step forward in our understanding of the universe, even though we have a great deal more to learn. I’m not ready to say that alternative ideas like LQG are garbage and have nothing worthwhile to contribute, let alone that global warming is a sham, but maybe Lubošification is a process that will happen to me one step at a time.

Granted, I'm not quite as radical (or rather, conservative) as Luboš on the quantum mechanics issue. I believe we still have a great deal to understand about ordinary, nonrelativistic QM in finite-dimensional Hilbert spaces—and as strong evidence for that claim, I cite the half-century that elapsed after QM's discovery before anyone asked the simple, profound question of whether or not it requires exponential resources to simulate on a digital computer. I believe it's at least possible that QM is only an approximation to a deeper theory, and that even wild speculations along those lines could deserve a hearing. I believe that philosophical arguments about the "meaning" of QM can be fun in moderation, and that mathematical theorems seeking to clarify QM's meaning can be illuminating—even if those theorems "merely make rigorous what we should've known all along." On all these questions, my impression is that Luboš disagrees.

On one crucial point, though, I stand shoulder to shoulder with Luboš. I believe that in science, the ratchet of progress only turns in one direction. If quantum mechanics is ever superseded, there's every reason to expect that its successor will be even more alien to human concepts, and less acceptable to the world's a-priori thinkers. (Has it ever been otherwise in the history of physics?) Likewise, if future generations do achieve a deeper understanding of QM than ours has managed, the path to that understanding will have to go "all the way through QM and out the other end." It certainly won't come from people suffering from infantile delusions about Bell's Theorem being wrong, or quantum phenomena being explainable by some doofus classical model that somehow escaped everyone's notice for the last century. Nor will it come from the aggressive ignoramuses whose interest in quantum-mechanical experiments starts and ends with the question of how to explain the experiments away. Instead progress will come, as it always has, from the scientists trying as hard as possible to turn the ratchet forward—maybe by pushing the known laws of physics up to Planck-scale energies (like Luboš and the other string theorists), or maybe by pushing the frontier of knowledge in other directions (like the ultimate limits of computation, to pick one random example).

And that, finally, brings me to my book. If one likes, Quantum Computing Since Democritus is my 400-page answer to a claim Luboš often makes: that nonrelativistic quantum mechanics has been completely understood since the 1920s, that all that's left is some grunt-work for engineers. To anyone who thinks that quantum computing is "merely" a cool application of century-old physics, that it doesn't raise any new questions about how our universe works—Quantum Computing Since Democritus is my answer.

In my book, quantum computing emerges as a particular kind of gadfly: one that doesn't challenge any aspect of quantum mechanics as (say) Luboš understands it, but that does spur us to ask a whole new set of questions about it. What kinds of questions? Well, here's a small sampling of what the book addresses:

"Why is quantum mechanics the way it is?" More precisely: what goes wrong if we try to base QM (say) on real numbers or quaternions rather than complex numbers, or conservation of 3-norm rather than conservation of 2-norm?

Can quantum computers solve NP-complete problems in polynomial time? Conversely, can quantum computers be simulated in the class NP? In other words, even assuming it's hard to simulate a quantum computer classically, is there at least a short classical proof that a QC produces such-and-such an output, which can be verified in classical polynomial time? Pending breakthroughs in theoretical computer science (like a proof of P≠NP), what kind of evidence can we give for or against these possibilities?

Is there anything "beyond" quantum computing? More precisely: is there any natural class of problems that generalizes what a quantum computer can do, but only "slightly" rather than "dramatically"? If there is, then can we find a hypothetical framework for physics that "slightly" generalizes quantum mechanics, and which would let us solve the problems in that class?

Can mathematical tools from quantum computing be used to solve problems about classical computing—much as complex numbers are often indispensable even for proving theorems solely about integers or real numbers?

Read anything written about quantum computing for a popular audience (or sometimes even a technical audience), and you'll probably find some claim of the flavor that a mere n qubits can store a whopping ~2n classical bits. In what sense is that actually true? How should we even define the "amount of information" in a quantum state? If we require that the information be "accessible via measurement," or "available to do useful computational work" (whatever that means), do we still find that the amount of information increases exponentially with the number of qubits? Are there problems that we can solve, or are there mathematical truths that we can verify, with help from a reasonable-sized quantum state but not with help from a reasonable-sized classical string? (Assuming we have a quantum computer available in both cases?)

Why does David Deutsch (one of the originators of QC) think that a scalable quantum computer would be a powerful demonstration of the truth of the many-worlds interpretation? What are the counterarguments to Deutsch's position?

How powerful would a quantum computer become if we augmented it with a closed timelike curve? Or what about "postselection" (the ability to measure a qubit and simply condition on the outcome being, say, |1〉)? Would a quantum computer interact with these sorts of powers differently than a classical computer would?

But the book is about much more than the above questions—indeed, half of it isn't even about quantum computing per se, but about what I view as the broad intellectual backdrop to QC. Among other things, the book covers set theory, first-order logic, Gödel's Theorem, Turing machines and computability, the P versus NP problem, modern cryptography, computational learning theory, interactive proofs, and all sorts of philosophical debates. In the last two chapters, I even venture ever-so-slightly onto Luboš's turf, sharing some thoughts about cosmology, holography, the black hole information problem, and firewalls, especially as they relate to quantum computing.

(The unusually-wide scope what I was trying to suggest with the strange title. Democritus, with whom the book really does start, was a Greek atomist known to his contemporaries as "the Laughing Philosopher"; he might have been the first human being to articulate what we'd recognize today as a scientific worldview.)

In terms of level, Quantum Computing Since Democritus has way too much math to be a "popular" book, but it's also too breezy and informal to be a textbook. So who's the intended audience? Basically, the sort of person who reads this blog! (Or my blog, or books like Lenny Susskind's The Theoretical Minimum or Roger Penrose's The Road to Reality.) I wrote the book for people who want to see part of the current scientific landscape from one researcher's heavily-biased vantage point—and who want that researcher to talk to them the same way he'd talk to a colleague in a different field.

So, I hope I've convinced you to give Quantum Computing Since Democritus a try. If I haven't, then maybe effusive reviews from three of the world's top quantum computing theorists will help seal the deal.

"Scott Aaronson has written a beautiful and highly original synthesis of what we know about some of the most fundamental questions in science: What is information? What does it mean to compute? What is the nature of mind and of free will? Highly recommended."

I laughed, I cried, I fell off my chair - and that was just reading the chapter on Computational Complexity. Aaronson is a tornado of intellectual activity: he rips our brains from their intellectual foundations; twists them through a tour of physics, mathematics, computer science, and philosophy; stuffs them full of facts and theorems; tickles them until they cry `Uncle'; and then drops them, quivering, back into our skulls. Aaronson raises deep questions of how the physical universe is put together and why it is put together the way it is. While we read his lucid explanations we can believe - at least while we hold the book in our hands - that we understand the answers, too."

"Not since Richard Feynman's Lectures on Physics has there been a set of lecture notes as brilliant and as entertaining. Aaronson leads the reader on a wild romp through the most important intellectual achievements in computing and physics, weaving these seemingly disparate fields into a captivating narrative for our modern age of information. Aaronson wildly runs through the fields of physics and computers, showing us how they are connected, how to understand our computational universe, and what questions exist on the borders of these fields that we still don't understand. This book is a poem disguised as a set of lecture notes. The lectures are on computing and physics, complexity theory and mathematical logic and quantum physics. The poem is made up of proofs, jokes, stories, and revelations, synthesizing the two towering fields of computer science and physics into a coherent tapestry of sheer intellectual awesomeness."

Dave Bacon, Google

In summary, I hope to have written a book from which anyone can learn something new about quantum mechanics—from my mom, to a precocious high-school student, to my computer-science colleagues, to (yes) my gracious host LM. Speaking of which: as a burying-the-hatchet gesture, I hereby offer Luboš a complimentary copy of my book, if he gives me an address to send it to. No letter-bombs, I promise.

Concerning the warming-communism link, I realize that I often point out the similarities but I can't resist to mention that you and people in "your camp" are much more likely to adopt a very naive, one-dimensional, black-and-white attitude to all such questions. But things aren't really that simple. You see Anna's comment below mine (you may soon see complementary, similar comments by Gordon Wilson). She would hopefully agree that she's left-wing but she's still a climate skeptic - for reasons that can't be reduced to simple ideological commandments.

Even when communism is concerned, I must say that communists did the worst things against the environment - it really sucked here when I was a kid. There was no widespread climate hysteria yet but they were already highly annoyed by NGOs like Greenpeace. Some communist officials' proclamations that we didn't need extra protests - the Greenpeace should go to clean a river instead - became sort of legendary. Only when communism collapsed, the environmental movement became a refugee camp for Marxists.

And even today, the Czech communist party isn't among the promoters of the climate hysteria, and our new president Zeman, a self-described leftist, is a climate skeptic, too. To decide which opinions about the future climate etc. are right, one has to do much more than to polarize all opinions to left-wing and right-wing. Your simplified proclamation behind the RNC microphone - but let me say, also the naive comments I have indirectly heard from Brian Greene and Ed Witten - suggest that you haven't thought about these matters independently and you decided about the answer via ideological keys - and I am talking about the two famous string theorists, too.

The book may be fun and I will read it if I get a copy ;-). But be ready that it's very likely (judging by your summary) that I will still view it as a moderate "anything goes"-type book. Well, if we look at your 7 "table of contents" points, I would probably write similar things about 1), the no-go theorems and rigidity of quantum mechanics, and about 5) and 6) i.e. the misinterpretations of the "exponential power" and "many worlds" character of quantum computers. I probably agree with 2), 3), 4) and expect you to know more than I do about these matters. Well, but in my picture, 7) would probably be included in 1), the no-go theorems: I would probably try to explain as well as I could that there can't be closed time-like curves and similar stuff.

Still, I must say that the summary of the book is "more conservative" than the preparing general comments about all the wonderful "loopholes" you want to be investigated and that I consider to be demonstrable fantasies and fallacies. Wouldn't you agree that this difference between the content of your book and your "quick conclusions about the space of ideas" suggests that if you try to write serious arguments supporting all these "loopholes" etc., you find out that nothing convincing can really be written about them, i.e. with a better resolution, it seems that my "more conservative" attitude is warranted?

Haha, great post Scott! On basis of this, I've ordered a copy of the book. You'd better not disappoint me otherwise I'll be sending a bunch of high energy twistors your way. And you wouldn't want that....

Actually, Democritus applied the doctrine of atoms to the question of the divisibility of space (in fact, probably it emerged from this study), and he was able to produce the right equation for the volume of a pyramid, a problem which was finally settled in http://en.wikipedia.org/wiki/Hilbert's_third_problem .

The spanish version of http://arxiv.org/html/physics/0006065 has an appendix with more quotes about the work of Democritus. This work of mine had a prequel about Zeno and a post-scriptum about the contacts with taoism, but I failed to notice the contact with jainism that you mention in your lectures (do you mention it in the book too?). Chinese sciences, at least chemistry and maths, seem to evolve from it.

You wrote that the goal of your post was to promote your book among the TRF readers.

It is then only fair to tell you how a TRF reader reacts on your post. I will start with your rant introducing the promotion.

First I thought it was a prank. But a prank is a joke, it should be funny at least on second degree. As what you wrote obviously doesn’t elicit a smile,it is extremely unlikely that it was meant as a joke and in the following I will assume that you meant it seriously.

IT'S HAPPENING, HUMAN ACTIVITY IS A MAJOR CAUSE, AND THE CONSEQUENCES ARESERIOUS!

Nobody here says that it isn’t happening. Even a cursory look at the Milankovitch cycles suffices to convince that we are in a warming part of the cycle and it is clearly not human activity which is thecause of the end of the last ice age like it won’t be the cause when the warming will revert to cooling somewhere in the future either. Human activity may induce a short transitory on a negligibly short time scale (e.g centuries) but the amount and the timing of the perturbation is not well understood anyway.

Trivially nothing follows from the above about “serious” consequences.Vaguely postulating that they are “serious” (for whom ? when ? how much ?) is the typical crackpottery that Lubos is often making fun of. I would say that 99% rational readers oppose precisely this postulate.

HE CAN'T ADMIT IT, BECAUSE HE ASSOCIATES CONCERN ABOUT GLOBAL WARMING – OR ANY OTHER "LEFTY" CAUSE – WITH THE EVIL COMMUNISTS WHO OPPRESSED CZECHOSLOVAKIA

Yes this is exactly what he does. And guess what ? He is perfectly right because he has something you don’t – namely long experimental evidence about predictions and laws that can be derived from such“lefty” ideologies and causes. And so do I. Do you know why the communists were evil ? Because they served (and some of them believed) evil “lefty” ideologies. That’s why Lubos’ commentson this field provide infinitely truer and sharper insights than yours will ever do

BUT SOME US DESPISE COMMUNISTS EVERY BIT AS MUCH AS LUBOŠ DOES

There is a fundamental difference between despising communists and despising communism (or Marxism or environmentalism etc). Communists are just people who put in practice communism.

Some were scary bastards but some were misguided and most were real idiots. What mustbe fought against and be despised is any form of communism.

As for communists, even Havel decided in 1989 against judging and hanging the guilty ones despite the fact that a good number would have deserved it. Since that spectacular failure of communism, most of the western communists disguised as environmentalists and anti capitalists but it doesn’t change their toxicity.

For such as you it is of course impossible to “despise” communists if you support the bulk of communist ideology. Be very sure that what you write and believe about the “fight” against global warming (or capitalism or markets or finance or philosophy etc) belongs to the bulk of communism/marxism. So your sentence quoted above is either a lie or evidence that you have not the slightest clue what you are talking about.

The typical ignorant excuse which drives me up the wall (and Lubos probably too) is in the line “There are many good ideas in communism but the implementation was bad”. Of course the truth is exactly opposite : “The communism in its whole is a criminal ideology but it was perfectly and consistently implemented.”

Now what was the purpose of my post? If you got so many things wrong, why should your book be better ? Or are you just a slow learner ? I am genuinely interested in the answer.

The blue team vs the red team is just a side show, Scott. The real tragedy is the Kabuki Theater that keeps Dems and Repubs fighting with each other as if there is ANY significant difference between them. The "The country is going to Hell, and it is because of Obama!" arguments are just as lame as the "The country is going to Hell because of Bush" fantasy was. As long as they can keep this idiocy alive, they can keep the masses distracted from the real issues. Yes, Bush tore up the Constitution, but Obama used the pieces for toilet paper. It is almost guaranteed the next President, REGARDLESS OF PARTY, will fish it out of the sewer and burn the scraps.

The ancient and worn out trick of "the other tribe is the enemy of our tribe" still works because people have still not evolved beyond the tribal stage.

It is like the cruise director of the Titanic staging a cockroach race to distract the passengers from the fact that the lifeboats are being taken by the crew. Of course the owners of the ship (Banks and Elite) were not so stupid as to get on board, knowing the ship was built so poorly. They did however make sure to tell the captain to loot the state rooms and fill any extra lifeboats with stolen goods rather than save any for paying passengers.

It's not about Left or Right. It's about Power and what works to serve Power. The rest is smoke and distraction.

hey lubos, enjoy your contrarianism to the quantum singularity [by the way, there are some scientists who actually *use that terminology* although scott is not quite yet "loopy" enough!]. so youve been gradually brainwashed by aaronsons endless blogging, alas. you havent been banned from commenting on his blog have you? guess you havent really challenged his mad scientist ramblings much then have you? I managed to get banned for a year from his blog after only a few comments. shew! quite a feat dont you think? talk about unfettered, no-holds-barred intellectual debate! you should step aside and let the *professionals* engage! scott is just stinging so bad because his fig-leaf 100K bet is easily exposed as the bogus rantings of a young, intellectually brittle polemicist..... verging on scientific bully.... which is evident in his endless blogs and not erased by the amusing stunt of posting on a supposed critics blog! but hey scott, quite the 3ring circus you've got going.... as always, enjoying the free entertainment! once again thx for that!

Hi, I've been banned at several blogs but I doubt Scott's was among them. Not sure what you mean by "quantum singularity". For me, it's a concept in science-fiction, not in science. In general, a singularity is a sign of a breakdown of a theory. A more complete theory that supersedes the singular one typically replaces the singularity by something regular or at least more well-defined and containing some information differing from a dull "infinity".

Cynthia, Earth and all that happens on it is not building afresh. Everything that is happening today has already happened many times before as far as human memory can go. Same old same old ;-)At least on TRF we are allowed to change the course of History... right ? ;-)

I expected a nice obituary for the Iron lady today and instead this poseur (flattered by Seth Lloyd's review LOL) showing his naivity in everything (from climate change to communism). Poor bastard, if you only had a clue...

Scott: I certainly will be getting your book---it sounds absolutely fascinating. I liked Vlado Vlatko's Quantum Information Theory. This sounds even more fun. Also, I hear secondhand that your talks are excellent (from my AI son, I think at Tahoe).Shake yourself free from the AGW groupthink enough to realize that intelligent "deniers" are not deniers. They could even be allies if they weren't all stereotyped and trashed. I could go into this in detail, but it is like Ouroboros. A straw man is constructed and attacked. I think most people here are in the Freeman Dyson camp about global warming---hardly deniers. Remember Bohr's quote --"Prediction is very difficult, particularly about the future.":)

Agreed, Cynthia, U.S. politics does seem staged.A scary thought is that with the economic mess, it may suit the U.S. to have a regional war with N. Korea to distract the plebs. I bet it is being discussed.

Scott, here is a post that was put on a communist web blog named "Kasama Project" by a blogger named Itznexcoyotl on a thread named "Maoist views on global contradictions"

It very clearly points out what climate alarmism is really about.

"I feel that, increasingly, the most successful movements are organizing in response to resource shocks and privatization of the environment (i.e. Naxalites & deforestation/drought, indigenous Americans & fossil fuel extraction/land appropriation, Filipino NPA & deforestation/fishing, etc)... The environmental movement is growing very quickly, and I see the most popular social struggles orienting themselves around "environmental justice" more and more. I think that this is potentially a critical opening, because it's not a very big intellectual leap from talking about liberal environmental justice to talking about land struggles/communizing land. In Portland, the housing justice movement has been able to use this language in order to open up more militant discussions about socialist revolution and expropriation among working class communities. Does anybody else see this, and has anyone else expanded more on this?"

Scott, I have no doubt that you have written a book just stuffed with profound intellectual content but I seriously doubt that you get the basics of QM or even comprehend the role of mathematics in physics. In your question #1 you imply that QM depends on its particular mathematical representation. I assure you that any representation that gives results in conflict with the standard ones is simply wrong and if a new representation is not in conflict then it is equivalent and will always give the same solution to any problem. It is also well established that there is no possibility of deeper mechanisms hidden within QM; this is just a fantasy. Finally, I invite you to give any scientific evidence that global warming is a serious problem. By “serious” I mean comparable in negative consequences to the other other obvious problems faced by humanity. The ball is in your court.

LOL, Colin, but no, Scott is right and you are wrong. It's a complimentary copy because it is donated as a compliment to someone. The word "complementary" also exists but it is something that balances something else, for example, momentum and positions are complementary variables on the phase space. The complement of a set A in a greater set B is composed of all the elements of B that do NOT belong to A. It's the "remainder", "complement", but that has nothing to do with complimentary copies.

The fact that a "Maoist blogger" named "Itznexcoyotl" (or someone else posting on "Itznexcoyotl's" blog?) had the idea of piggybacking on the environmental movement to promote communism, doesn't strike me as strong evidence that that's "what climate alarmism is really about." Bill Gates, Warren Buffett, the insurance industry, and US military planners are also quite worried about the impacts of climate change. Are they closet Maoists as well?

> Is there anything "beyond" quantum computing? More precisely: is there any natural class of problems that generalizes what a quantum computer can do, but only "slightly" rather than "dramatically"? If there is, then can we find a hypothetical framework for physics that "slightly" generalizes quantum mechanics, and which would let us solve the problems in that class?

Yes! Quantum gauge theories with indefinite norms for unphysical states. Can chiral gauge theories be simulated on a quantum computer in polynomial time?

the book looks great, covers some really interesting subjects which I agree are not finalised just yet. I'll probably get the paperback edition (the kindle edition is slighly cheaper but will undoubtedly look goddamn awful)

However, I think you will lose your $100,000 bet, but the reason will not be too disappointing.

I see that Scott was recently quoted in a nytimes article with a critical comment regarding D-Wave. Could he explain what D-Wave is making? I doesn't seem like a quantum computer in the "traditional" sense. What, if anything, is their machine useful for?

Well, I would personally say that complex numbers are much more fundamental in QM than they are in electrical engineering etc. where they're just a convenient tool that helps us with a theory of fundamentally real quantities...

In the reference I gave, it explains why the only coherent strategy for QM is to use complex numbers. The core of the explanation is that the n-qudit state would be described by the same number of parameters as thetensor product of n single qudits. So you have no choice, and QM is very special. In other scientific domains, you can use quaternions (image processings) or real, but not in a coherent QM.

On "global warming" and the ridiculous oxymoron "climate change" I have to say that I, as an experimental particle physicist ( retired) spent the equivalent of a masters thesis time into delving in the claims of the IPCC ( all 800 pages of the physics justification) and am absolutely convinced that the computer models are useless for predictions because of the sloppy assumptions within them . In addition there are seven important observations where data contradict their predictions. A model is falsified with one contradiction.e

Most of the polls that have brain washed the institutes you enumerate are biased. Of course there is warming after the little ice age. The point is there is no proof of anthropogenic warming being large and overwhelming.

Many of the "scientists" are eating at the CO2 trough, as well as the businessmen.

Time will show, but in the meantime little children will die from stupid economic policies.

I will post this here, because I don't want to infest Scott's blog with aphid-like posts.The thing that gets me riled about consensus climatescience pronouncements that "there IS NO DEBATE" is that if this were true, it would place climate science in the same reliability category, as, say, quantum mechanics.Climate science is highly unreliable because it is a swamp of parameters and chaotic systems and relies on big data. The people doing the research may be doing their best with the training they have, but "NO DEBATE" is just a bullying, polemical statement.

As a long time follower of Shtetl-Optimized, I have really enjoyed the intellectual framework of your "Quantum Computing since Democritus" lectures and I look forward to purchasing and reading your new book.

However, I must say that I was embarrassed for you after reading the all-caps scolding you directed our way. Thanks to the hard work Lubos puts in, the followers of "The Reference Frame" are probably some of the best informed when it comes to: 1) The actual global temperature measurements and trends, 2) The contribution of CO2 to those trends, 3) The consequences of slightly higher temperatures and CO2 levels, and 4) The absence of any plausible theory whereby we are in danger of runaway AGW.

Well said, my respect for spending/wasting your time to explain something so obvious. Infantine citizens such as Mr. Aaronson are an easy prey for various seductive ideologies - be it climate hysteria or socialism/communism.

@SA Your childish example of how you found that communism is evil... a camp for boyscouts or whatever? Are you serious? Is this an example of how you interpret the world around? You are a silly person living in a fantasy. You have no idea what the life was in Eastern Europe before '89. There is estimated 80 million victims of your fun ideology (including Asia and Latin America) plus a countless number of otherwise destroyed lives. It's disgraceful how you dare to talk about something you don't understand.

That's interesting Anna, I've never personally looked at the models or the stats to have an opinion on the worth of the predictions (I'm *not* the prof. Philip Jones from University of East Anglia, who famously presided over some screwed up models BTW!)

I've had tons of posts about D-Wave on my blog! Briefly: D-Wave is trying to build a special-purpose computer for adiabatic optimization. *If* it worked, then eventually it should be able to solve various practical optimization problems at least somewhat faster than we know how to solve them with a classical computer. (How much faster? That's a big question to which we don't know the answer! The issue is that the adiabatic algorithm, like simulated annealing, is a "heuristic" algorithm that isn't guaranteed to work. A general exponential speedup is almost certainly too much to hope for, but maybe a quadratic speedup is not.) The D-Wave machine would be specialized for heuristic optimization: it wouldn't help (for example) for running Shor's algorithm to factor large numbers in polynomial time. Anyway, that's the idea. So far, my personal assessment is that, while D-Wave has demonstrated that(a) their machine can indeed solve the special-purpose optimization problem (Ising spin minimization) that it's designed for quite well, and

(b) their machine involves quantum effects, at least at the level of individual Josephson junctions,they have not yet convincingly demonstrated that such quantum effects as are present in their device are playing any causal role in solving the optimization problem faster. This is the main reason why people have been hesitant to describe their device as a "quantum computer." But maybe D-Wave *will* be able to demonstrate this in the future -- I certainly hope so!In the meantime, press coverage of D-Wave has been consistently TERRIBLE, with the articles regularly overhyping or outright falsifying what they've done, and presenting D-Wave's interactions with companies like Google and Lockheed as "all the proof needed" that the underlying scientific claims are valid. That's what motivated me to invest as much time as I did writing skeptical blog posts, and feeding skeptical quotes to reporters. I don't know why John Markoff wrote the particular article you saw -- there seemed to be no actual "news" to report, just rewarmed old stuff.

An interesting thing about the United States, Gordon, is that it holds freedom of speech above all other freedoms. Therefore, ideas are ALWAYS out there.

Control is manifest not through overt censorship/physical impediments, etc., but instead through allowing the individual to become consumed with themselves and the various distractions employed to this end.

When confronted by fast food, unlimited internet porn, sports 24/7 x 1000, alcohol, drugs, you name it, the average Joe cannot be so concerned with political corruption, economic fraud, and the rest, until it is too late to do much about it.

But, this is not to say that the problems have not been elucidated for decades. Look at the anti-Fed battle that Ron Paul has carried forward in the House for the past 30 years. People couldn't care less because they were too busy stuffing themselves with hot dogs and beer and aunt Millie’s barbecue.

Despite the plethora of information available, most people are still in denial. But this is human nature, as most people simply wish to be left alone to go about their lives. The Elite well-understand this tendency and exploit it at every turn.

The only difference between now and the years of old, is now they can say in the open what they are doing, i.e., the Fed admits it's punishing savers and manipulating interest rates, and the people are too stupid to know what the consequences are so they can do it freely and openly.

LOL, if you get anoint yourself and Lubos "professional climatologists," then I hereby do the same for myself! (And Ed Witten, Steven Weinberg, Murray Gell-Mann, Stephen Hawking, and just about every other physicist I can think of, with the partial exception of Freeman Dyson. All professional climatologists, and all hold a climatological opinion diametrically opposed to yours!)

"The waves in quantum mechanics had to be complex, "exp(ikx)", for the waves to remember the momentum as well as the direction of motion. "As usual right on. QM cannot do without i. Using i l QM tells us all of what may be without requiring that we decide what is before it was. Nothing could be more fundamental than telling us what can become real and what can't with such simplicity.

It is sad that a scientist decides about what are after all measurement against prediction matters, par excellence the scientific method, with such a statement. Physics is not about voting. Theory describing data is not a consensus matter. Data trumps theory every single time in the scientific method. A list of Popes in physics will not prove that quarks are composite if data does not say it.

I have been belaboring this issue for a long time and it no longer interests me scientifically, like a course learned and finished. Up to now each year I give a lecture for aspiring graduate students in my old institute and the list of contradictions go up to 7.

Here is a link http://wattsupwiththat.com/2009/02/17/britains-lessons-from-the-winter-of-2008-2009/#comment-86163 with links where I consider the IPCC models' predictions and their failures. This is from 2009 and the list of falsifications stops at 4 , but even this is enough.

After reading this I would be somewhat afraid to get less than I bargained for if I buy this (your) book. IOW: The style and content of the guest-blogged article put me off slightly. Lumo has set my expectations so high that few TRF-guest-bloggers will be able to make an impact on me that I find very rewarding (in whichever way) - though it has happened!

Actually, for me, Aumann's Agreement Theorem formalizes the intuition that you should take other people's subjective assessments as seriously as your own---at least, to whatever extent you have separate grounds to regard the other people as honest and rational. The basic reason is that, while you can indeed examine the evidence yourself and form your own opinion, those others have presumably done the same---and their honest opinions serve as powerful summaries of everything they've learned.

So for example, I don't believe in supernatural phenomena simply because billions of other people do---because I don't have grounds to see the people who believe in those things as particularly rational. But when I find that the most honest and rational people I can think of---and Weinberg, Gell-Mann, etc. are included---hold an opinion diametrically opposed to mine on some complicated empirical question, then at the least I'm profoundly troubled by that fact. If I decide to hold on to my own opinion, then it's only after long reflection, and after my confidence in my opinion has been weakened.

Some people would say this attitude makes me a spineless intellectual coward. I say it makes me tend to converge to the right answers.

Ironically, I went through something like that process in regard to string theory. The physicists and mathematicians whose opinions I most respected on other grounds, were so nearly (though not completely) unanimous in saying that the technical achievements of string theory dwarfed those of loop quantum gravity, that I eventually decided I was almost certainly wrong to place the two programs on a similar footing. Of course, learning more about string theory, from Brian Greene and others, also helped! But I'm not the slightest bit embarrassed about the role other people's opinions played. (Note that my own judgments certainly entered into the meta-question of deciding which people's opinions to trust.)

The thing is, I could sort of understand the climate skeptics if they'd gone through a similar process. That is, if they'd noticed that maybe 95% of the world's most accomplished scientists (not "Popes" or "authorities," but the experts with the best track records of being right) were arrayed against them, spent many sleepless nights troubled by that fact, and finally decided to hold on to their original opinion anyway. But they don't even seem troubled. Instead, they seem to view the opposition of the world's Weinbergs and Wittens (not to mention thousands of lesser scientists) as a badge of honor -- the same way the armchair physicists who deny relativity and quantum mechanics do. And that's what makes me part ways with them completely.

This might surprise you, but I'm not under the idiotic delusion that having my candy taken away by camp counselors is even remotely comparable in gravity to the horrible murder of 80 million people by Communist regimes (or, let's say, to the Holocaust, which claimed most of my extended family). These things differ in magnitude as an apple differs from the Earth. On the other hand, it's by understanding the apple that Newton learned the general principles that govern the Earth's motion. In the same way, I tend to think that it's from our childhood experiences that we all form our first ideas about evil, and even the seeds of our later political views. Of course, we could very easily have formed the wrong ideas that way! For me, the solution is to openly acknowledge (and consciously reflect on) the impact of our childhood experiences, so that we can better decide which lessons we want to keep and which we want to discard.

You misunderstand me. I am speaking as a scientist and a physicist with over forty years experience in fitting data to theories. When I started, QCD was a gleam in some people's eyes and the great Feynman himself was against it. Nevertheless, I fitted the data available to me with the QCD model and found the famous parton model inconsistent. It took many experiments and a lot of statistics to go from high p_t inconsistencies to the validation of QCD as a theory for hadrons, and the Pope of that time had to reconsider his opinions.

I started by believing the hype of AGW, the six meters rise in sea level made me start digging in at predictions versus data, because it would turn my vacation cottage into a beach front property!! When I started digging into the IPCC models it was just out of curiosity. It fast turned into a horror, I was walking around pulling my hair, when I saw the sweeping generalizations and wrong tools and generalizations used by these GCmodels to predict catastrophies a la the Revelation. That is when I started searching for blogs that discussed the matter.

Physics is not about consensus and results in observational physics should always be gauged against the maxim: "correlation is not causation".

A true physicist is always skeptical of claims he/she should check and become satisfied that the claims are valid, otherwise declare agnostic on the ones he/she does not want to spend the time checking on. Not become a partisan of a cult because everybody knows that "the sun goes around the earth"..

As for the physicists' names you enumerate as endorsing AGW I would like a link. Have they signed a statement? or what?

The statement which you include in your response is not saying anything else than "decisions should be made on the basis of the best scientific results available" and nothing else. It doesn't focus only on the climate change (in fact there is only one paragraph making references to climate). Hence I am not surprised that so many people signed this a rather general statement...The fact that you say "the statement he signed talks explicitly about climate science" is a good example of the way everything about the climate change is extremely exaggerated to the point of hysteria.

I watched GellMan. I agree with Lubos. Even his simple arithmetic has little meaning, because he presumes that the anthropogenic factor is huge. Why? somebody told him so. And three factors entering climate? I would say 33.

noname, I find your reasoning rather lawyerly. The entire motivation for that statement was the belief, on the part of the signers, that the Bush administration was systematically skewing science in a right-wing direction, especially (though not exclusively) by downplaying the reality and seriousness of human-caused climate change. Now, I suppose that doesn't *logically* imply a belief about the underlying issue of climate change itself. But I note that Lubos, who (unlike most of us) knows Witten, didn't seem to hesitate in making the inference.

This sounds like an infantile appeal to authority. I would imagine that Weinberg and Hawking are busy enough with their own research and don't spend much time studying "climate change". Besides that, just because Weinberg was good at QFT does not make him a deity whose opinion on every subject should be worshipped. I could care less what Weinberg or anyone else thinks, I only care what the data says - there was a modest rise in temperature which has stopped for many years now. Its extremely difficult to weed out how much of that rise was due to simply exiting the "little ice age", how much is due to factors like cloud cover and how much is due to CO2, and anyone who seriously believes that "climate change" in the form of a one or two degree rise in average temperature is such a great threat perhaps needs a return to communism and fascism or a great depression so people can relearn what real threats are in life. Hysteria over climate change is a disease of prosperity.

The two parties bend together and “merge” at the very top because they serve the same masters. It’s a God damn shame how they are able to exploit the nation’s legitimate cultural, as well as scientific, differences to get away with it with ongoing plunder.

The gate-keeping at DailyKos reminds me of the gate-keeping at RedState, National Review and The American Conservative. Kos’s and Erick Erickson’s “we need to support the lesser of two evils” arguments are damn near interchangeable. Just swap out a few particulars. It’s eerie.

You apparently decided to close your eyes and ears and stubbornly refuse to understand what we are saying.

I don't expect you to agree, for that you know too little (sofar), but genuinely try to understand what we are saying instead of exhibiting this autistic like mantra « La, la, la I didn't hear anything »

I was not saying that every scientist knew what climatology was about. I was saying that every good physicist could understand everything about climatology if he was ready to invest some months in reading papers and blogs about climate.

See the difference ?

Hell you can even use real size GCMs available on line if you feel like that and many of us skeptics indeed did so.

Therefore many readers of this blog, starting of course with Lubos and continuing with Annav or myself are familiar with « climatology » at the level of what you call « professional climatologists »

The question whether we publish is irrelevant. There are many blog posts here or on climate related blogs (Climate Audit, ClimateEtc, Blackboard etc) that have the quality of « climatology » papers.

I gave you a link to a real climatology paper so that you realize how simple and naive most of them are but, of course, you didn't read it.

There are also many examples where initial blog posts were later expanded to published climatology papers but often people look at this domain more like a hobby. This is definitely my case.

In contrast you don't box in the same category. You were apparently never interested in getting some information for whatever mysterious reason. Do you really belong to this kind of people who are said « The mankind will be wiped out in the next 1000 (or 100) years by global warming unless you repent and do as I say. » and xho just believe and do as being said ?

If yes it strikes me as being completely irrational.

And before you say that the above quote is a carricature, think again. It is exactly what Hawking is saying in the link you gave us.

By reading/listening to the links you provided it appears clearly that Witten, Gell Mann &Co know about climate exactly as much as you do – namely nothing. Of course that they could learn fast and probably become much more skeptical in the process but obviously they didn't do so.

That's why these links regardless of the famousness of the names tell me exactly nothing. An accumulation of similar links would be just mindless propaganda and changeexactly nothing about my opinion. I only listen to people who demonstrably know what they are talking about be it skeptics or warmists. And then I use my own knowledge to sort them out.

I insist and repeat : the skeptics differ from the warmists less in the science than in the evaluation of consequences of a modest temperature increase in 1 century or more.

TonVonk, is there anyone who you'd acknowledge as a climatology expert, and who more-or-less agrees with the consensus of (the people who most of the world calls) "climatologists"? Fine, not James Hansen, not Michael Mann ... *anyone*? If there isn't, then it seems to me that, in order to "understand what you're saying" about the necessary conditions for climatology expertise, you DO expect me to agree with you first about the underlying issue.

"The absence of any plausible theory whereby we are in danger of runaway AGW."

Oh, that sideshow. Aaronson said "serious" and "concern", you claim he said "danger" and "runaway AGW" (runaway greenhouse - Venus)?

Serious would be devaluing of beach properties, the need to eventually move people away from NY (say), and the concern is that it costs a lot. The ongoing concern is that the increased costs from AGW related climate events in US already costs more than it had cost US to contribute to prevent that level of AGW in the first place, AFAIK the numbers and the evidence for the AGW cause.

Not all nations are as unlucky (and some likely more), but increased, unnecessary costs is *a serious concern*.

Same goes for the observed species migrations as the climate zones change, some will benefit, other will loose and temporarily (say, for a million year or so) decreased species diversity is *a serious concern*. (We benefit a lot from diversity and the drug & food potentials they give. Again, an economical situation if you like.)

Scott, You may be “profoundly troubled” when Weinberg, Gell-Mann etc. hold a view contrary to yours but that has nothing to do with science. They may be right or you may be right. So what?A good scientist simply ignores every opinion, including his own, and seeks the truth. Clearly, you have not done that, at least, not yet.

I agree, Lubos, but would you not agree with me that complex numbers are fundamental in an even deeper sense, if that’s possible. I cannot imagine mathematics without complex numbers. Such a math would be but a shadow of the real thing. As you know, my expertise is in solid-state physics, a field that could not even exist without complex numbers.

I sincerely apologize for misreading your blog, Scott, but I don’t think you were as clear as you might have been for a casual reader like me. I thought that you were talking about the world that we actually live in. If I had not been so thoroughly put off by your asinine, capitalized rant on global warming i would have been more careful; I am sure. I have heard so many of these alarmist diatribes than I am pretty well inured to them. They are disgusting and an affront to to any thoughtful person. Incidentally, I am not a left-winger. I am a registered Republican but I consider myself to be an Eisenhower Republican, an endangered species, unfortunately.I am but a old physicist and a rather poor mathematician who knows almost nothing about your field of expertise. Your book would be a major intellectual challenge for this senescent brain.

Yes, Shannon, we have been here before and Cynthia is just being Cynthia. My country is not going down the tubes. I expect, in fact, that the US will have a larger influence on this old world over the next few decades than it has had during the last few decades. Of course we have problems but every other developed country has worse problems. We have been described as the best house in a bad neighborhood. It’s not a bad analogy. But, at the very worst, this century is going to be a whole lot better than the last one for us humans.

Gene, what you've described is not the thought process of a scientist, but rather the thought process of a crackpot scientist with a Galileo complex --- the kind who email me P=NP proofs and refutations of quantum mechanics every week! A good scientist tries to get the right answer by integrating ALL relevant information. That includes the results of experiments you've done yourself and arguments you've invented yourself ... but also the published literature, and the views of the scientists who've thought hardest about the subject or who generally have the most stellar records of being right, especially when they tell YOU that you're wrong (which we should always acknowledge the possibility of). Of course the relative weights of all these factors depends on your own expertise. For example, when a Nobel particle physicist (who I won't name) told me that he saw no reason why physical systems shouldn't be able to solve NP-complete problems in polynomial time, I didn't feel the slightest hesitation in contradicting him. But that's only because I *knew* I'd studied the subject more thoroughly than he had, and also knew that virtually everyone who'd studied it as much as I had, had reached the same conclusion as me.

Come on, Scott, and calm down. Gene's achievements - in much more tangible scientific enterprise - surely don't give you a justification to compare him to crackpots.

What Gene correctly says is that the opinion of people who haven't really studied the discipline properly and impartially is *not* a part of the relevant information that a scientist includes to make his own conclusions. And that's true despite famous surnames such as Witten etc.

These guys just know next to nothing about the climate and even if and when they know something, it's beaten by their decision to remain in a certain predetermined ideological straitjacket. At any rate, what they say is worthless for a scientist who actually wants to reach the conclusions within the scientific method.

TomVonk, thanks for this comment -- I *also* feel like I'm being seriously engaged for the first time in this discussion.

Your comment contains what I regard as an astonishing admission: that "2 scientists who agree on 99% of the science can disagree 100% about the consequences"---and that if I understood the science, I would probably find myself "somewhere in the large spectrum of opinions about the consequences" (well, I guess it would be hard to find myself NOWHERE in the spectrum!).

Does this mean that, by your own lights, many of the "warmist" scientists are NOT scientifically mistaken (or rather, at most 1% scientifically mistaken)---and the issue is just that they hold "political and philosophical preferences" that differ from yours?

Let me go further: suppose I'm the President of the US, and suppose my advisers tell me there's a completely new kind of airborne bird virus that's rapidly mutating to infect humans. Among expert virologists and immunologists --- who actually AGREE about 99% of the science --- there's a large spectrum of opinions about the consequences, depending on the experts' political and ideological preferences. A sizable faction thinks the virus could spread so rapidly and prove so fatal that it will wipe out human civilization entirely, as smallpox wiped out Native American civilizations. Another faction thinks there's no danger whatsoever. Most experts fall somewhere in the middle -- for example, speculating that the virus will ultimately be contained after it's killed a "mere" 100 million people.

Now suppose my advisers also tell me that there's a proven technological route to developing a vaccine---*but* it would cost several trillion dollars and require unprecedented international cooperation. On the other hand, the project would probably have all sorts of technological spinoffs (as, say, the Allied victory in World War II did), and the requisite technologies would probably eventually need to be developed anyway---if not for this virus then for the next one. They ask me whether I want to authorize the vaccine project now, or whether I want to wait and see whether the doomsayers can prove the dangers more solidly (at which point, of course, it might be too late).

Maybe others would respond differently -- but in this hypothetical situation, I'd want to say the same thing as Churchill did, when he received a letter signed by Alan Turing about the chronic underfunding and bureaucratic obstruction of British codebreaking efforts at Bletchley Park. "Make sure they have all they want on extreme priority. I want to see action this day!"

Gene, I do like the American positive thinking. French should learn from you guys on this. This century will be better than the previous ones as long as humans manage to keep some Judeo-Christian values imo.

I once had the same view as yourself regarding climate change, Scott. What really turned me around was a careful study of tidal-gauge data, which show very clearly that the SQRT(2) increase in CO2 has had no measurable effect on sea levels. Tidal gauge measurements are individually clouded by tectonic effects as regards velocity (rise rate) but they are much more sensitive to acceleration (increase of rise rate) because flows in the mantle are slow and steady. If you look carefully you will conclude, as I have, that any increase in sea level rise rate over the past few decades or centuries (look at archeological records as well) is probably less than 0.1 mm/year = 0.4 inches per century. Since the background rise rate is slowing, as it always does in an interglacial period, it is highly probable, in fact, that the rise rate is actually slowing a bit despite man-made global warming, which is undeniably real.

Of course projecting past results into the future is always questionable but it is unreasonable to imagine any mechanism that would cause a dramatic increase in rise rate. About two thirds of the current rise rate is due to thermal expansion and one third is due to melting land ice. Both of these are very steady processes and not subject to orders of magnitude increases. The projected danger from rising seas is greatly exaggerated, to say the least.

You and I share Berkeley PhD’s, Scott, and I would love to have the opportunity to talk with you. I could learn a lot but you might learn a bit from me, as well.

By the way, you are surely wrong in imagining a deeper level in QM. This has been a key topic on TRF for years and I am totally in Lubos’ camp on this. There is simply nothing missing in QM. Nothing.

Thanks for the defense, Lubos; I really didn’t phrase my comment well at all. Of course I take seriously opinions of people that I deem to be experts in the field at hand. Nonetheless, science is not a democracy and voting is irrelevant. The majority can be wrong even if they are considered to be at the top of their profession.

You and I both hold Berkeley PhDs, Scott, but I have thirty plus years more experience in the real world than you do. I don’t doubt your skills in your own field and you would be foolish to doubt mine.

What you are missing, I think, is the skepticism that comes from experience. Everyone, absolutely everyone, is capable of fooling himself and that is exactly what you have done.

My working experience in QM exceeds fifty years and I assure you that when you talk about a deeper level in QM you are having a fantasy.

I hope you don’t lose your respect for Weinberg, Gell-Mann and the others, Lubos; they deserve credit for their accomplishments. We are all human and prone to self-delusion, even the smartest and most successful of us. We have to be a bit forgiving, don’t we?

Gene, please don't patronize me. I'll put my "pro-QM record" up against anyone's; I've spent much of the decade arguing against the many people who think quantum computing can't work because QM "obviously" has to break down when you get to hundreds or thousands of arbitrarily-entangled particles. I've happily pointed out the many existing experiments they're at risk of contradicting, and the immense difficulty of finding any theory that agrees with those experiments but *wouldn't* allow things like quantum computing. On the other hand, would I be willing to bet my life that, 10,000 years from now, no significant modification of QM will have been discovered, in regimes far from those that anyone has yet tested? No, simply because I wouldn't express that kind of confidence about *any* scientific theory -- not even about QM, arguably the most solid and hard-to-modify one we know. That's, if you will, "the skepticism that comes from experience."

It might be interesting if you forgot what you "know" about anthropogenic global warming and look at this series of plots describing the temperature over millenia from the ice core records. For me it is humbling in how insignificant the little red blade of Mann et al ( lets suppose it is correct) is between the sweeping changes in temperature from the time humanity came out of Africa, to now. And the second feeling is that I can be a prophet, we are sliding into the next ice age in, as the gypsies say, three terms :). ( a term can be a week, a month, a year, and for this prophecy hopefully a millennium).

I confess that I really don’t understand what you are talking about, Scott. Perhaps age has dimmed my imagination. I thoroughly support your questioning of anything and everything, including quantum mechanics. The fact that QM is immutable does not mean that you should bow down to it and hold it sacred. It is not for me to say what insights might or might not arise from questioning QM. I really don’t know if quantum computing will become a reality but I sure wouldn’t bet against it.Most of the evils on this planet, if not all of them, have happened because people stopped questioning, because questioning itself became unacceptable, because it became “blasphemy”. Now there is a word that I truly despise and I’m sure you do to. Now, I plead with you, Scott, to take that skepticism with you when you think about global warming, which, upon careful consideration, is, almost certainly, a substantial benefit for mankind. You, too, will learn to love CO2.

Late to the party, sorry. This was a good guest blog because Prof. Aaronson took the time to sit down with his readers and discuss.

Unfortunately what should have been the main topic -- quantum mechanics and Aaronson's new book -- got overshadowed by the controversy over his opening remarks on catastrophic anthropogenic global warming (CAGW), misleadingly named by him as just "global warming".

I am heartened by my impression that the critics, chiefly Tom Vonk, appear to have made a dent in Aaronson's previously unquestioning acceptance of the CAGW memes... although it may be a long time before there will be a perceptible shift in attitude.

As a non-scientist, I must try to reduce the complexity to manageable proportions. For me, it is all about sensitivity, i.e., the increase in global mean temperature that will follow from a doubling of atmospheric CO2. I find the assumptions (so-called "positive feedbacks") that CAGW proponents use to plug numbers into their simulations that will double, triple or quadruple sensitivity to be unpersuasive, and their behavior in "selling" their climate models to the public is alarmist fearmongering.

If I may, a tip for Prof. Aaronson. More people will buy your book if you not only lay out a précis of the key points you discuss in it but actually offer a mini version of (some of) your argument, complete with examples, human-interest stories, visual content, etc. It won't lose you any buyers. Trust me on this.